Season 7 of Doctor Who is a fan favourite, probably because of its taking itself terribly seriously (unlike the more fun later seasons of the Pertwee era). This season does have some great elements to it, especially the snarky and intelligent companion Dr Liz Shaw, the early and rather more prickly version of the Brigadier, and Jon Pertwee playing the Doctor far more straight than at any other time in his run.
It’s also a season which has provided a great deal of inspiration to the 2005- version of the show, featuring the debut appearance of both the Autons and the Silurians, and a rare example of a parallel universe (a narrative ploy also used for great effect in New Who).
What I hadn’t quite twigged until the DVD release of The Ambassadors of Death, the third of four stories featuring the Third Doctor with his UNIT-and-Liz-Shaw ensemble, is that this season also used the masked figure of astronauts as creepy figures of horror, something which has been something of a feature of several Steven Moffat-written stories, and the River Song arc in particular.
(Hey, who turned out the lights?)